Liquidus temperature of a steel is calculated from its chemical composition according to the so far proposed procedures by simply summing up the iron melting point lowering effects of all in the steel contained elements Xi, as they are given by approximating the iron liquidus curves with the straight lines in the corresponding binary Fe-Xi systems. The intensification of the iron melting point lowering effect with the increasing concentration of each element contained in the steel has not been at all or only partly taken into account in this approach. This is the reason why the calculated steel liquidus temperatures are not accurate enough. In the here proposed new calculation procedure the iron melting point lowering effect of an alloying element Xi is first translated into an equivalent effect of carbon in the Fe-C system by converting the concentration of Xi into an equivalent concentration of carbon taken as a reference element. The carbon equivalent iron melting point lowering effect of all elements contained in the steel including carbon is then evaluated by summing up the calculated equivalent carbon concentrations of all elements together with carbon into a fictitious total equivalent carbon concentration. A so calculated total equivalent carbon concentration has made it possible to determine with a good accuracy the steel liquidus temperature along the stable Bla or y liquidus lines in the Fe-C system. The success of a melting point calculation is strongly dependent on the accuracy of the equivalence factor equations for each alloying element. They are derived by relating the iron liquidus line in the binary Fe-Xi system to that in the Fe-C phase diagram.
The microsegregations in iron alloys can be thoroughly described in detail by a microprobe analysis. By determining the element contents on a surface (max. 100.100 points of measurement) the elements segregation behaviour in the structure can be examined. Adequate data evaluation such as three‐class‐diagrams, coupling of contents during the precipitation of cored crystals or line‐scans give further evidence of the amount of segregations in the cast or rolled material. In conjunction with other methods such as thermal analysis, the microprobe analysis is able to give information about the solidification of iron alloys.
Isothermal holding tests were carried out on the Fe-Ni-Cr system in the two-phase region between the melt and crystal in order to determine the I and 6 liquidus surfaces in the iron-rich corner, to establish the position of the peritectic line running between them, and to compare the results with those contained in relevant literature. The initial contents of the 13 test series were staggered in roughly equal intervals from 29.6% Ni and 12.9% Cr to 18.7% Ni and 28.4% Cr. They were held between the temperatures of 1450 and 1530 °Cat intervals of 10 °C for 40 minutes in each case, so that 93 liquidus concentrations and temperatures were determined. Both liquidus surfaces can be described very accurately with corresponding mathematical equations and mathematically intersected in order to determine the course of the peritectic line. The results enable sufficiently accurate development of the melting equilibria of the entire ternary system, building on the basis provided by the known I and 6 liquidus lines of the three binary systems. Schmelzgleichgewichte in der eisenreichen Ecke des Systems Fe-Ni-Cr. Im System Fe-Ni-Cr wurden isotherme Halteversuche imZweiphasengebiet zwischen Schmelze und Kristal! durchgefuhrt, um die 1 -und 6-Liquidusflachen in der eisenreichen Ecke zu bestimmen, die Lage der zwischen ihnen verlaufenden peritektischen Linie festzulegen und mit den Ergebnissen des Schrifttums zu vergleichen. Die Anfangsgehalte der 13 Versuchsreihen waren in ziemlich gleichen Abstanden gestaffelt (29,6% Ni und 12,9% Cr bis 18,7% Ni und 28,4% Cr). Die Proben wurden in Abstanden van je 10 °C zwischen 1450 und 1530 °C 40 min gehalten. Daraus resultierten 93 Liquiduskonzentrationen und -temperaturen. Seide Liquidusflachen lassen sich mit entsprechenden mathematischen Ansatzen genau beschreiben und zur Festlegung des Verlaufs der peritektischen Linie mathematisch zum Schnitt bringen. Aufbauend auf den bekannten 1und 6-Liquiduslinien der drei Randsysteme lassen die Ergebnisse die Entwicklung der Schmelzgleichgewichte des genannten Systems mil geni.igender Genauigkeit zu.
New literature results on the liquid equilibria in the three edge binary systems make necessary a reconsideration and correction of liquidus surfaces of the γ and δ solid solutions hitherto outlined in the literature. Therefore, with respect to the critically reinterpreted edge binary systems, the shape of the stable liquidus surface of the γ and δ solid solutions has been newly outlined.
Isothermal holding tests were carried out in the Fe‐Ni‐Mo system in the two‐phase region between the liquidus (melt) and the solidus (crystal). The δ and γ liquidus surfaces in the iron‐rich corner of the Fe‐Ni‐Fe3Mo2‐NiMo subsystem, as well as the position of the peritectic line situated between them, could be very accurately established by the experimentally determined isotherms. Based on these results and on the known liquidus lines in the three boundary binary systems, as well as on the known concentration fields of the Fe3Mo2‐NiMo solid solutions, the melting equilibria could be developed with sufficient accuracy in the entire subsystem.
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